1. Field of the Invention
The present invention relates to an optical lens, an optical package having the optical lens, a backlight assembly having the optical lens, a display device having the optical lens, and a method thereof. More particularly, the present invention relates to an optical lens capable of improving a luminance uniformity and a color uniformity, an optical package having the optical lens, a backlight assembly having the optical lens, a display device having the optical lens, and a method of emitting uniform light from a backlight assembly.
2. Description of the Related Art
Liquid crystals of a liquid crystal display (“LCD”) device vary arrangement in response to an electric field applied thereto, and a light transmittance of the liquid crystals is changed to display an image. Because the LCD device is not self-emitting, it requires a light source to display the image. The LCD device displays the image using an externally provided light or an internally provided light.
Examples of the light source include a light emitting diode (“LED”), a cold cathode fluorescent lamp (“CCFL”), a flat fluorescent lamp (“FFL”), etc. A large screen LCD device includes the CCFL and the FFL. A small screen LCD device includes the LED.
The LED, in general, has a substantially quadrangular chip shape from which the light is generated. The LED is a substantially point light source. The light generated from the LED is distributed in a Lambertian distribution.
FIG. 1A is a perspective view showing a Lambertian distribution of a light generated from a point light source. FIG. 1B is a plan view showing the Lambertian distribution shown in FIG. 1A.
Referring to FIG. 1A, the Lambertian distribution of the light generated from the point light source has a substantially spherical shape. A distance between the point light source and one point on a surface S of the spherical shape corresponds to an amount of a light on the one point at an angle formed between a vertical line and a straight line from the point light source to the one point of the surface S.
A volume of a cone formed by the point light source and a portion of the surface S is substantially proportional to an amount of a light passing through the portion of the surface S.
Referring to FIG. 1B, an area of a contour formed by the point light source and a portion of a circumference C is substantially proportional to the amount of the light passing through the portion of the circumference C.
A distance between the point light source and the portion of the circumference C reaches a maximum value at the vertical line. The distance between the point light source and the portion of the circumference C reaches a minimum value at a horizontal line that is substantially perpendicular to the vertical line. The distance between the point light source and the portion of the circumference C at an oblique light that forms at an angle of about 45° with respect to the vertical line is about 70% of the maximum value. An area of a contour that is formed between angles of about 0° to about 45° with respect to the vertical line is about 80% of an entire area of the circle.
That is, in the Lambertian distribution of the point light source, a vertical portion of the light is larger than a horizontal portion of the light. Therefore, a luminance uniformity and a color uniformity of a display incorporating a backlight assembly having the point light source are deteriorated.